True/False
Indicate whether the
statement is true or false.
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1.
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Work is measured in joules.
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2.
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The unit of power is the watt.
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3.
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The thread around a screw is a lever.
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Multiple Choice
Identify the
choice that best completes the statement or answers the question.
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1.
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Which of the following, by scientific definitions is NOT work?
a. | lifting boxes of books | b. | pedaling on your bike | c. | holding a book over
your head | d. | pushing a chair across the room |
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2.
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Distance is measured in _____.
a. | meters | c. | Joules | b. | kilograms | d. | Newtons |
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3.
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Power is work divided by _____.
a. | time | c. | distance | b. | force | d. | speed |
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4.
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Karla does 25 J of work in 5.0 s carrying her clean clothes upstairs. How much
power did Karla use on the clothes?
a. | 125 W | c. | 5.0 W | b. | 100 W | d. | 4.0 W |
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5.
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A carpenter applies 475 N to the end of a crowbar. The force exerted on the
board is 950 N. What is the mechanical advantage of the crowbar?
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6.
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A worker applies a force of 20 N to pry open a window that has a resistance
force of 500N. What is the mechanical advantage of the crowbar?
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7.
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Find the force needed to lift a 2000N rock, using a jack with a mechanical
advantage of 10.
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8.
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You exert an input force on a hammer. The hammer exerts a(n) _____ force on the
nail.
a. | input | c. | horizontal | b. | friction | d. | output |
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9.
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Joe is using a crowbar to remove a tree stump. He applies 2066 J of work to the
crowbar. The output work of the crowbar is 1240 J. What is the efficiency of the crowbar?
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10.
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A dressmaker is cutting fabric. She applies 18 J of work to the scissors. The
scissors apply 15 J of work to the fabric as it cuts. What is the efficiency of the scissors?
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11.
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The wheel and axle on a wagon is a simple machine. The radius of the wheel is
0.12 meters. The radius of the axle is 0.03 meters. What is the ideal mechanical advantage of the
wheel and axle?
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12.
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A slanted surface used to raise an object is a(n)____.
a. | efficiency board | c. | inclined plane | b. | effort ramp | d. | wedge |
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13.
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A bar that is free to pivot about a fixed point is a ____.
a. | fulcrum | c. | ramp | b. | lever | d. | wedge |
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14.
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The rate at which work is done is called ____.
a. | efficiency | c. | force | b. | effort time | d. | power |
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15.
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The work output of a machine divided by the work input is the ____ of the
machine.
a. | efficiency | c. | power | b. | effort | d. | resistance |
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16.
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The amount by which a machine multiplies an input force is called the
____.
a. | efficiency factor | c. | mechanical advantage | b. | fulcrum | d. | resistance
force |
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17.
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An inclined plane wrapped around a cylinder post is a ____.
a. | lever | c. | screw | b. | ramp | d. | wedge |
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18.
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A winding mountain road is an example of a(n) ____.
a. | lever | c. | wedge | b. | inclined plane | d. | wheel and axle |
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19.
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When two or more simple machines work together, they are called a(n)
____.
a. | compound machine | c. | screw | b. | effort machine | d. | simple machine |
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Completion
Complete each
statement.
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1.
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Machines make a task _______________.
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2.
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A machine’s mechanical advantage is the ratio of the _______________
exerted to the _______________ applied.
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3.
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Power describes the ____________________ at which work is being done.
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4.
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The pivot point of a lever is called the ____________________.
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Matching
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Match each simple machine with the machines below. a. | inclined plane | d. | lever | b. | wedge | e. | wheel and axle | c. | screw |
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1.
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knife
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2.
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leaf rake
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3.
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potter's wheel
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4.
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threaded bolt
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Short Answer; worth 2 pts each. Write in complete sentences for full
credit.
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1.
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How are work, time, and power related?
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2.
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A 700-watt gasoline engine and a 300-watt electric motor both do 3 J of work.
Which machine can do the work faster? Explain your answer.
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3.
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Give one example of a compound machine and list the simple machines that make it
up.
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4.
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Explain how your teeth work as a wedge.
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5.
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A force of 825.0 N is needed to push a car across a parking lot. Two students
push the car 35.0 meters. How much work did the students exert on the desk?
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Problem; worth 2 pts. extra credit each. SHOW YOUR MATH and PUT UNITS
for full credit.
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1.
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You use 200 N of force to push a snow shovel 10 m along the ground. How much
work was done?
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2.
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How much power is needed to do 1,000 J of work on a box if it takes 50 s to lift
it?
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3.
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How much work is done if 500 W of power is used over 2 min?
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Essay; worth 4 pts. extra credit. Write in complete sentences and
support your answer with concepts learned from this chapter.
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1.
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The six types of simple machines all make work easier. Describe, using examples,
the three ways in which machines make work easier. Then, identify the relationship between input work
and output work for all machines.
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